Temperate plants show a rapid seasonal turnover in various leaf traits and defenses. Such trends in plant defenses can potentially drive seasonal shifts in the specialization of insect herbivores. We quantified how non-volatile leaf metabolites, inducible volatile organic compounds (VOCs), C:N ratio and leaf toughness changed between the early, middle, and late seasons in five Salicaceae species and one Salix hybrid. We also explored seasonal trends in overall trait variation among the studied plants. We tested whether seasonal changes in dietary specialization of leaf-chewing larvae and adult beetles related to changes in the studied host-plant traits. Trait turnover occurred mainly through changes in VOCs and seasonal increase in traits that directly lower herbivore feeding efficiency. The overall variation in leaf traits was highest in the early season, with seasonal intraspecific variation being 33% smaller than the variation among species sampled at one time point. Although less frequently than we expected, the two groups of insect herbivores showed seasonal changes in specialization. The significant trends in herbivore specialization included peaks in the middle season for larval specialization based on VOCs and host phylogenetic relatedness and for adult beetle specialization based on C:N ratio plus leaf toughness. The detected species-specific trends in host-plant traits, their intraspecific variability, and differential trends among insect herbivores highlight the importance of considering seasonal variation when predicting trends in plant-herbivore interactions.

• Klíčová slova
• Chemical defenses, Leaf toughness, Salicinoids, Tannins, Volatile organic compounds,
• MeSH
• brouci fyziologie   MeSH
• býložravci * MeSH
• larva fyziologie   MeSH
• listy rostlin * MeSH
• roční období MeSH
• Salicaceae * MeSH
• těkavé organické sloučeniny MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• těkavé organické sloučeniny MeSH

Plants employ diverse anti-herbivore defences that can covary to form syndromes consisting of multiple traits. Such syndromes are hypothesized to impact herbivores more than individual defences. We studied 16 species of lowland willows occurring in central Europe and explored if their chemical and physical traits form detectable syndromes. We tested for phylogenetic trends in the syndromes and explored whether three herbivore guilds (i.e., generalist leaf-chewers, specialist leaf-chewers, and gallers) are affected more by the detected syndromes or individual traits. The recovered syndromes showed low phylogenetic signal and were mainly defined by investment in concentration, richness, or uniqueness of structurally related phenolic metabolites. Resource acquisition traits or inducible volatile organic compounds exhibited a limited correlation with the syndromes. Individual traits composing the syndromes showed various correlations to the assemblages of herbivores from the three studied guilds. In turn, we found some support for the hypothesis that defence syndromes are composed of traits that provide defence against various herbivores. However, individual traits rather than trait syndromes explained more variation for all studied herbivore assemblages. The detected negative correlations between various phenolics suggest that investment trade-offs may occur primarily among plant metabolites with shared metabolic pathways that may compete for their precursors. Moreover, several traits characterizing the recovered syndromes play additional roles in willows other than defence from herbivory. Taken together, our findings suggest that the detected syndromes did not solely evolve as an anti-herbivore defence.

• Klíčová slova
• Gallers, Leaf-chewers, Plant–herbivore interactions, Salicinoids, Specialized metabolites,
• MeSH
• býložravci * MeSH
• fylogeneze MeSH
• listy rostlin MeSH
• Salix * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Evropa MeSH